Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $194.54   5.368%   $204.9829   $204.98   $205.00   $205.00  
  Purchase #2 $157.49   7.416%   $169.1695   $169.17   $169.15   $169.20  
  Purchase #3 $59.25   8.388%   $64.2199   $64.22   $64.20   $64.20  
  Purchase #4 $193.60   12.687%   $218.162   $218.16   $218.15   $218.20  
  Purchase #5 $73.46   8.126%   $79.4294   $79.43   $79.45   $79.40  
  Purchase #6 $231.82   13.765%   $263.73   $263.73   $263.75   $263.70  
  Purchase #7 $236.75   10.230%   $260.9695   $260.97   $260.95   $261.00  
  7 purchase totals = $1,146.91       $1,260.6632   $1,260.66   $1,260.65   $1,260.70